Method and apparatus for the rocking compaction of refractory metal powders

ABSTRACT

A method and apparatus for compacting refractory metal powders into ingot form by means of an hydraulically operated curved blade which is progressively rocked across a mold containing loose refractory metal powder to compact that powder into usable ingot form.

P. A. LlVERA 3,814,788 METHOD AND APPARATUS FOR THE ROCKING COMPACTION June 4, 1974 OF REFRACTORY METAL POWDERS Filed NOV. 24 1971 2 Sheets-Sheet 1.

v 9 N oi P. A. LIVERA 3,814,788 METHOD AND APPARATUS FOR THE ROCKING COMPACTION Jung 4, 1974 OF REFRACTORY METAL POWDERS 2 Sheets-Sheet 2 Filed Nov. 24 1971 United States Patent Office Patented June 4, 1974 Int. Cl. B22f 3/02 US. Cl. 264-111 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus for compacting refractory metal powders into ingot form by means of an hydraulically operated curved blade which is progressively rocked across a mold containing loose refractory metal powder to compact that powder into usable ingot form.

BACKGROUND OF THE INVENTION Heretofore, certain refractory metal ingots, i.e., tungsten and molybdenum ingots were manufactured from metal powder in twenty-four inch lengths. To press a tungsten or molybdenum twenty-four inch ingot from powder, it required the near full force of a single action 250 ton press. The pressing of larger ingots was almost prohibitive since the total force required with a single action press is directly related to the size of the ingot being pressed, and presses in excess of 250 tons are not economically feasible. Green ingots of a greater length than twenty-four inches are, of course, desirable because the many processing steps required in the transformation of a pressed green ingot into tungsten or molybdenum wire can be more expeditiously and economically accomplished with a longer ingot.

There has been a continuing search by the metal pressing industry to develop a method by which larger ingots could be pressed from refractory metal powders without the use of enormous single-action presses. Several methods have been attempted such as, for example, stepped compaction where the powders are incrementally compressed by progressive lateral movement of a stepped compressin blade. Another method which has been employed is the use of angled punch presses where the compressing blade has a flat portion and an angled portion with the blade being sequentially brought against the powder with the powder being moved laterally relative to the press between each subsequent compacting stroke of the compacting blade. Although many of these processes have been found suitable for the compacting of ceramics and metallic powders such as nickel, austenitic stainless steel and low alloy steel powders, they have not proved to be suitable for the compacting of refractory metal powders such as tungsten and molybdenum.

SUMMARY OF THE INVENTION This invention relates to a method and apparatus for the continuous compacting of refractory metal powders, and more particularly, to the continuous compaction of tungsten and molybdenum powders into green ingot form. In practicing this invention, the metal powders are placed in a mold form, which is located on the bed of an hydraulic press which carries a curved rocker blade between two hydraulic cylinders. One end of the curved blade is placed in contact with one end of the powder in the mold form, and a compressive force is applied to that end of the curved blade to compress the powder in contact with the blade. The hydraulic pressure is then gradually reduced in the first end of the curved blade while it is gradually increased at the other end of the curved blade to cause the curved blade to rock across the surface of the powder and continuously compact the powder into green ingot form as it traverses the length of the mold.

In an alternative embodiment of this invention, the refractory metal powder may be disposed in a mold form which is longer than the curved blade of the press, and the curved blade may be cyclically applied to the loose powder with the mold form being shifted between the cycles to thereby compact a green ingot of a length greater than that of the curved blade of the press.

BRIEF DESCRIPTION OF THE DRAWINGS Many of the attendant advantages of this invention will become more readily apparent and better understood as the following detailed description is considered in connec tion with the accompanying drawing, in which:

FIG. 1 is a schematic illustration of a press constructed in accordance with this invention and capable of practicing the method of this invention;

FIG. 2 is a side elevational view of the press and mold form employed in this invention;

FIG. 3 is a schematic illustration depicting the compacting of metal powders in accordance with this invention; and

FIGS. 4 through 6 are schematic illustrations of an alternative embodiment for practicing the method of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in detail to the drawings, wherein like reference characters represent like parts throughout the several views, there is illustrated in FIG. 1 a schematic view of a rocking compactor, or press, constructed in accordance with this invention and generally designated 10. The press structure includes a base or bed 12, upstanding supports 14 mounted to the base 12 and carrying at their upper ends the upper superstructure 16 of the press. A pair of hydraulic cylinders 18 and 20 are fixedly mounted in spaced relationship on the overhead superstructure 16. Piston rods 22 and 24, respectively extend from the cylinders 18 and 20 and are hinged at 26 and 28 to the compacting rocker blade 30. The rocker blade 30 includes an arcuate or curved edge or surface 31.

A rapid release mold of the type disclosed in copending application Ser. No. 201,907, titled Rapid Release Mold, filed the same date as this application by Phillip A. Livera, now issued as U.S. Pat. 3,734,658 and owned by the assignee of this application, is situated on the press bed or base 12 beneath the curved surface 31 of rocker blade 30 and has contained therein the refractory metal in powder form. In accordance with this invention, the rapid release mold 32 may have a powder containing area the same length as the rocker blade, or the powder containing area within the rapid release mold 32 may be in excess of the rocker blade length for purposes of practicing an alternative embodiment of this invention.

\ As pointed out previously, the production of refractory metal ingots from tungsten or molybdenum powder requires tremendous pressures in terms of pounds per square inch. In the past, ingot size has been limited because of this force requirement and, in fact, a single action 250 ton press is required to press a 24 inch bar. In accordance with this invention, since only small increments of the powder are pressed at any one time, pressures on the order of 30,000 to 40,000 psi. are all that need to be developed by the press to compress an ingot twice as large as the standard 24 inch bar by employing the current four foot rocker blade and the method of this in vention. In the alternative embodiment of this invention a six foot or longer ingot can be pressed with sufficient green ingot strength for further processing.

The rocking press of this invention may be automatically operated by employing a conventional tape-actuated pulse generator 36 to actuate a pair of stepping motors 38 and 40, which in turn, respectively control pressure regulating valves 42 and 44. Each of the hydraulic cylinders 18 and 20 are separately actuated by their own closed system pressure supply with the maximum line pressure developed being approximately 3,400 p.s.i. The closed pressure system for actuating hydraulic cylinder 18 includes the pressure regulating valve 42, which is sup plied with hydraulic fluid from the reservoir 50 by means of the pump 46. The stepping motor 38, in response to a predetermined signal from the pulse generator 36, con trols the position of the pressure regulating valve 42, hence the flow of pressure to the hydraulic cylinder 18. Complementarily, but separately, the hydraulic cylinder 20 is controlled by the pressure regulator valve 44, which is positioned by the stepping motor 40 in response to signals from the pulse generator 36 to control the amount of hydraulic pressure to the cylinder 20 from the reservoir 52 and pump 48. Back pressure to each of the hy' draulic cylinders 18 and 20 is provided by the air system 54.

In the simplest form of this invention, illustrated in FIG. 3, the hydraulic cylinder 18 is actuated by the pressure regulator valve 42 in response to signals from the pulse generator 36 with the full 3,400 p.s.i. line pressure while pressure is applied through the hydraulic cylinder 20. In this initial stage of the compacting process the metal powder 34 in the left-hand end of rapid release mold 32 is compacted with the full 30,000 to 40,000 p.s.i. pressure for only a small increment at the left-hand edge. As the operation proceeds, the pulse .generator 36 causes the stepping motors 38 and 40 to slightly reposition the pressure regulator valves 42 an 44 to cause the pressure in hydraulic cylinder 18 to slowly decrease while the pressure in hydraulic cylinder 20 gradually increases, thus causing the rocker blade 30 to rock across the surface of the refractory metal powder 34 with the total 30,000 to 40,000 p.s.i. output pressure moving gradually from left to right, as viewed in FIGS. 1 and 3, across the curved surface 31 of the rocker blade, and hence incrementally compress the refractory metal powder into green ingot density. At the conclusion of the stroke, 30,000 to 40,000 p.s.i. of output pressure will have been transferred from the left-hand edge of the refractory metal powder across the entire length of the powder surface and be finally applied at the righthand edge of the rocker blade 30. As will be apparent, the total output pressure applied by the hydraulic cylinders 18 and 20 when added together will at all times equal substantially a constant and thereby produce uniform compaction of the metal powders throughout the length of the ingot.

At the conclusion of the pressing cycle the pressure in both hydraulic cylinders is removed thus raising the rocker blade and the green ingot is subsequently removed from the mold form 32 in the manner described in the above-identified copending application Ser. No. 201,907 now issued as US. Pat. 3,734,658.

A six foot ingot can also be compressed in a six foot mold with a four foot rocker blade. The process for progressively compacting a six foot ingot in a six foot mold with a four foot rocker blade is best illustrated in FIGS. 4 through 6. Initial compaction is identical with the compaction of a four foot ingot in a four foot mold in that the left-hand edge of the blade commences to compact the left-hand end of the powder with full pressure in cylinder 18 and no pressure in cylinder 20. The pulse generator operates stepping motors 38 and 40 to respectively control pressure regulator valves 42 and 44 to cause the rocker blade to rock, through an increase in hydraulic pressure in cylinder 20 and a complementary decrease in hydraulic pressure in cylinder 18, across the surface of the powder until the rocker blade has transferred maximum compressive force from the left-hand edge of the 4 blade across the surface of the powder for a distance of three feet or three quarters of the length of the blade. At this point, the rocker blade is lifted through the reduction of pressure in both cylinders, and the mold form shifted two feet to the left. Pressure regulators 42 and 44 are then adjusted so that the lowest point of the rocker blade is now one foot from the left-hand edge of the blade, which is now positioned over the middle of the mold form, three feet from each end of the mold. In this position, 25% of the 30,000 to 40,000 p.s.i. pressure is provided by the hydraulic cylinder 20 an 75% by the hydraulic cylinder 18. The pulse generator is then reactivated to cause pressure regulator 42 to gradually decrease the hydraulic pressure in cylinder 18 while pressure regulator valve 44 is operated to gradually and complementarily increase the pressure in hydraulic cylinder 20, thus causing the rocker blade 30 to proceed to compress the remaining three feet of partly compressed or uncompressed powder to a fully compressed ingot form.

Although six foot ingots are ideally suited for the continuous processing of refractory metal ingots into wire, it will be apparent that the process employed to compact a six foot ingot with a four foot rocker blade could be continuously repeated to thereby compress refractory metal powders into green ingots of lengths of eight feet, ten feet, twelve feet or even greater lengths. It will also be apparent that other mechanical, hydraulic and electrical systems can be substituted for the hydraulic system illustrated schematically in FIG. 1, in order to cause the uniform transfer of pressure from one hydraulic cylinder 18 to the other hydraulic cylinder 20 to thereby cause the rocker blade to progressively rock across the surface of the loose powder to incrementally compact the powdered metal to green ingot form.

What is claimed is:

1. The method of compacting metal powders into ingot form comprising:

filling a mold form with the metal powder to be compacted;

placing one end of a curved blade in contact with the metal powder at one end of the mold form;

applying a vertical compressive force to the said one end of said curved blade to compress the powder in contact with said one end of said blade;

simultaneously decreasing the vertical compressive force on said one end of said curved blade while applying and increasing a vertical compressive force to the other end of said blade to cause said blade to rock across the surface of said powder, and thereby compress all of said powder into ingot form.

2. The method of compacting metal powders into ingot form according to claim 1, wherein the compressive force applied to one end of said curved blade when added to the compressive force applied to the other end of said curved blade at all times equals substantially a constant.

3. The method according to claim 2, wherein said constant force produces a constant pressure of between about 30,000 and 40,000 p.s.i.

4. The method of claim 1 wherein said blade is rocked for a portion of its length; lifted from said powder, said mold is shifted in the direction of said one end of said rocker a distance less than that which has already been compacted, said blade is returned to its initial angular position, and the curved blade rocked for the remainder of the length of said mold.

5. An apparatus for progn'essi'vely compacting refractory metal powders contained in an enclosed mold form into a green ingot, said apparatus comprising:

a press bed having a plurality of support members extending upwardly therefrom and supporting an overhead superstructure;

a pair of spaced hydraulic cylinders mounted on said overhead superstructure;

hydraulically, vertically actuated piston rods extending from each of said hydraulic cylinders;

a curved rocker blade pivotally mounted adjacent each of its ends to said piston rods; and

means connected to said hydraulic cylinders for applying and controlling a first hydraulic pressure to one of said hydraulic cylinders and applying and controlling a second hydraulic pressure to the other of said hydraulic cylinders.

6. An apparatus according to claim 5, wherein said means for applying and controlling hydraulic pressure to each of said hydraulic cylinders includes a pressure regulator valve controlled by a stepping motor in response to pulses generated by a pulse generator.

7. An apparatus according to claim 6, wherein the said means for controlling the hydraulic pressure to each of said cylinders causes the cumulative pressure applied by both of said cylinders to be at all times substantially uniform.

8. The method of compacting metal powders into ingot form comprising:

filling a mold form with the metal powder to be compacted;

placing one end of a curved blade of a length less than said filled mold form in contact with the metal powder at one end of said mold form; applying a vertical compressive force to the said one end of said curved blade to compress the powder in contact with said one end of said blade;

simultaneously decreasing the vertical compressive force on said one end of said cur-ved blade while applying and increasing the vertical compressive force to the other end of said blade to cause said blade to rock across the surface of said powder for a portion of the length of said powder,

lifting the curved blade from the partially compressed powder,

shifting said mold form a predetermined distance With respect to said curved blade,

repositioning said curved blade into contact with said partially compressed powder; and

again decreasing the compressive force on said one end of said curved blade while simultaneously increasing the compressive force to the other end of said curved blade to cause said curved blade to rock across the surface of the remainder of said powder and thereby compress all of said powder in said mold form into ingot form.

9. The method of compacting metal powders into ingot form according to claim 8, wherein the compressive force applied to one end of said blade when added to the compressive force applied to the other end of said curved blade is at all times equal to a constant.

10. The method according to claim 9, wherein said constant force produces a constant pressure from between about 30,000 and 40,000 p.s.i.

References Cited UNITED STATES PATENTS 3,571,849 3/1971 Kirk 425-77 3,103,038 9/1963 Zolton 425-78 3,464,348 9/1969 McGlinchey -295 2,994,917 8/1961 Fritsch 264-111 3,130,761 4/1964 Fleming et a1. 100-295 3,231,373 1/1966 Marshall 264-111 3,158,474 11/1964 Andersen et a1. 264-111 3,157,914 11/1964 Deibel et a1. 42577 2,784,453 3/ 1957 Hjulian 425-78 2,509,354 5/1950 Jones et a1. 100-295 2,195,683 4/1940 Ross et a1 100-295 FOREIGN PATENTS 1,150,263 6/1963 Germany 425-78 ROBERT F. WHITE, Primary Examiner J. R. HALL, Assistant Examiner US. Cl. X.R. 264-; 425-78, 419 

